JPH0465338B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a thermal expansion coefficient measuring device for automatically measuring the hot linear expansion coefficient (hereinafter referred to as the thermal expansion coefficient) of ceramics at high temperatures in a non-contact manner and with high accuracy.

The coefficient of thermal expansion of ceramics, especially refractories, is an extremely important characteristic that serves as a guideline for determining the expansion allowance of refractories lining furnaces used in hot conditions.

Conventionally, thermal expansion measurement has been carried out using a contact method (Fig. 1) or a non-contact method (Fig. 2) as specified in JIS R2617 and 2207. The displacement detection rod 3 is brought into contact with the sample 2 placed on the sample holder 4 installed in the furnace 1, and the expansion and contraction of the sample is thereby detected, and this displacement is read by a dial gauge or by a differential transformer displacement measuring device. 6 or the like, or recorded on a recorder 7, and after the measurement, the displacement was read from the curve and the expansion coefficient was calculated. In addition, in Figure 1,
5 is a differential transformer, 11 is a heating element, and 12 is a thermocouple.

However, in this method, a detection rod is brought into contact with the sample and measurement pressure is applied, so if the sample shows a softened state at high temperatures, the sample itself will deform due to the compressive force caused by the measurement pressure, making it difficult to measure the true expansion coefficient. is difficult. In addition, in this case, it is often necessary to correct the difference in the amount of expansion between the sample holder and the displacement detection rod, which causes errors.

Therefore, at present, a method of measuring without contacting the sample to be measured is adopted. As a non-contact measurement method, as shown in FIG. 2, there is a method in which the displacement of both ends of a sample 2 placed in a heating furnace 1 is artificially read using a telescope 10 with a scale. This method is
When the temperature inside the furnace is high, it is difficult to see the difference in brightness between the sample and the atmosphere, making it difficult to read and relying heavily on experience, which causes measurement errors. In addition, it was necessary to calculate the rate of change of the obtained data relative to the original length of the sample, and to plot the relationship between temperature and expansion rate. In FIG. 2, 8 is a thermometer, 9 is a lighting device, 11 is a heating element, and 12 is a thermocouple.

Another method is to photograph the displacement of the sample at each temperature with a camera equipped with a scaled telephoto lens.
There is a method of reading the displacement of a sample from a photograph, but it requires time to process the data and is problematic in terms of efficiency.

The present invention enables highly accurate and automatic measurement in order to improve the above-mentioned drawbacks.

That is, the thermal expansion coefficient measuring device of the present invention automatically measures the displacement of a sample by combining two sets each of a displacement measuring device and an illumination device each consisting of a camera with a built-in solid-state scanning light-receiving element and combined with a lens system and a camera control unit. It is something to do.

That is, the device of the present invention: It is a non-contact type that measures without contacting the Γ measurement sample.

It is configured to convert the displacement of the measurement sample into an electrical signal using a solid-state scanning photodetector camera equipped with a Γ telephoto lens and an infrared filter.

When the Γ sample reaches a high temperature, the sample itself emits infrared rays, but an infrared ray removal filter is used to compensate for the decrease in sample displacement sensitivity of the solid-state scanning photodetector camera.

In the present invention, the "solid-state scanning light-receiving element" is a Charge Coupled Device (CCD), and the present invention uses a licensor camera in which a CCD self-scanning one-dimensional photo diode is arranged on the imaging plane of a lens, and This device converts the brightness of the image of the subject into an electrical signal and extracts it as a pulse signal for output voltage measurement.

Further, the infrared ray removal filter is a filter that transmits wavelengths in the visible light region, for example.
This is a filter made by SCHOTT that transmits light with a wavelength in the range of 350nm to 800nm.In the device of the present invention, it is continuous from room temperature to high temperature (1600℃) by removing infrared light generated in the furnace at high temperatures. This makes it possible to measure the expansion coefficient.

As shown in FIG.
The dark area where the light is blocked by the sample 2 and the bright area where the light directly reaches are enlarged and projected onto the surface of the solid-state scanning light-receiving element using a lens, and the displacement is measured from the ratio of the bright area L to the dark area D.

In this case, each solid-state scanning photodetector camera 15
At the same time, a pattern corresponding to the size and brightness of the image of the sample 2 is displayed, and measurement values are averaged. The outputs of the control unit 16 are added together and output as a digital output signal corresponding to the displacement. By using a program created using this output and the digital signal output of the digital thermometer 19 using a general method, the control unit 16 and the BCD (Binary
data acquisition, calculation,
The data is inputted to a microcomputer 18 that performs storage and output, and the data is stored and calculated, and a digital plotter 20 is used to plot the relationship between temperature and coefficient of thermal expansion as a curve.

In the device of the present invention, the telephoto lens 14 that reads minute displacements of the sample 2 needs to be installed away from the heating furnace to prevent the influence of heat.
mm, F number 5-8 is good. If the working distance is shorter than this, the telephoto lens 14 will be placed close to the high-temperature heating furnace 1 for measurement, resulting in measurement errors due to the influence of temperature. Also, if the F number is larger than this, it will be difficult to obtain the amount of light necessary for measurement, and if the F number is smaller, the lens diameter will become larger. It cannot be measured unless it is long.

The telephoto lens 14 used for this purpose is
In addition to working distance and brightness, it is necessary to increase the lens magnification to approximately 10x in order to satisfy the measurement resolution of 1 μm.

As a countermeasure against this, the device of the present invention uses a compound lens system to increase the lens magnification x 10 times and the working distance.
We solved this problem by producing a 300-500mm telephoto lens 14.

On the other hand, the sample 2 in the heating furnace 1 emits infrared rays from itself when the temperature reaches 1000°C or higher. It is also sensitive to emitted infrared rays. Further, the amount of infrared rays emitted from the sample 2 increases in proportion to the fourth power of the temperature, as the temperature increases.

As shown in the waveform of the oscilloscope shown in Figure 3, there is a bright area L that shows the sensitivity of the solid-state scanning photodetector due to the light from the illumination device 9, and the light from the illumination device 9 is blocked by the sample 2, but is emitted from the sample 2. It is difficult to distinguish between the dark area D, which shows the sensitivity of the solid-state scanning photodetector using infrared rays, and it is difficult to measure displacement at high temperatures.

To solve this problem, we investigated various filters that remove infrared light, and used a filter that completely removes infrared light emitted from sample 2 without reducing the amount of illumination.

According to the present invention, as shown in the waveform of the oscilloscope shown in FIG. 4, the light from the illumination device 9 indicates the sensitivity of the solid-state scanning photodetector, and the light from the illumination device 9 is blocked by the sample. Since the infrared rays emitted from the oscilloscope are removed by the filter 13, an oscilloscope waveform with a clear difference between the dark area D and the bright area L, in which the solid-state scanning light-receiving element exhibits no sensitivity, is obtained.

The filter 13 removes light with a wavelength of 0.8 μm to 1 mm in the infrared region, and preferably has a high light transmittance in order to obtain sufficient contrast and light intensity for measurement. In this case, one filter does not need to remove wavelengths in the entire range of 0.8 μm to 1 mm, and two or a combination of two or more filters may be used.

The illumination device 9 needs a sufficient amount of light to provide sufficient contrast from low to high temperatures on the light receiving element surface. Light sources include incandescent bulbs, xenon lamps,
Halogen lamps, laser beams, etc. can be used, but it is better to use an incandescent light bulb in combination with a voltage regulator because the equipment is simple and easy to handle. In either case, the light should preferably be collimated using a condensing lens and should have straight propagation, and the diameter of the beam should preferably be 10 mmφ or more at the sample surface and the brightness should be 100,000 nt or more.

An example of measurement using the apparatus of the present invention will be explained below.

Example: Silica brick sample, width 20 mm x height 15 mm x length 85
A telephoto lens 14 with a working distance of 480 mm and an F number of 8 and a glass filter 13 that removes light with a wavelength of 0.8 μ to 1000 μ in the infrared region are set in the heating furnace 1 of the apparatus of the present invention shown in FIG. Figure 6 shows the relationship between temperature and coefficient of thermal expansion by capturing data every 5 degrees Celsius from room temperature to 1500 degrees Celsius using a heating rate of 4 degrees Celsius per minute.

As described above, the minimum reading accuracy is achieved by combining a camera using a solid-state scanning photodetector, a telephoto lens, an infrared ray removal filter, and a known computer.
We have succeeded in developing a thermal expansion measuring device that can measure the thermal expansion coefficient with high accuracy from low to high temperatures at 1 μm, and the industrial effect is remarkable.

[Brief explanation of drawings]

1 and 2 schematically show a conventional thermal expansion coefficient measurement method, FIG. 3 shows an example of an oscilloscope waveform using the conventional method, and FIG. 4 shows an example of an oscilloscope waveform using the apparatus of the present invention. FIG. 5 is a schematic diagram showing the arrangement of an example of the device of the present invention, and FIG. 6 is a graph showing an example of the relationship between temperature and coefficient of thermal expansion obtained by the device of the present invention. In the figure, 1: heating furnace, 2: sample, 3: displacement detection rod, 4: sample holder, 5: operating transformer, 6: displacement measuring device, 7: recorder, 8: thermometer, 9: lighting device ,
10: Telescope with scale, 11: Heating element, 12: Thermocouple, 13: Filter, 14: Telephoto lens, 1
5: solid-state scanning photodetector camera, 16: control unit, 17: microcomputer interface, 18: microcomputer,
19: Digital thermometer, 20: Digital plotter, 21: Oscilloscope.

Claims (1)

[Claims] 1. Two sets of illumination devices are installed on one side of the sample heating furnace, and on the opposite side, two sets of telephoto lenses with an F number of 5 to 8 and a working distance of 300 to 500 mm and a 0.8 μm to
A thermal expansion coefficient measuring device characterized in that a camera control unit connected to a solid-state scanning photodetector camera and an oscilloscope equipped with a filter for removing infrared rays of 1 mm wavelength is connected to a computer and a digital plotter.